The present invention relates to a temperature display device of a vehicle, which displays a temperature of coolant of an engine.
Generally, thermostats are provided in engine cooling systems where coolant is circulated between an engine and a radiator. This type of engine cooling system is formed with channels extending from the engine and returning to the engine, including a channel through the radiator and a channel bypassing the radiator. The channel to be used is switched by opening/closing the thermostat, thus the circulation state is switched between a first state in which the coolant of the engine is circulated through the radiator and a second state in which the coolant is circulated bypassing the radiator.
As the thermostat provided in the engine cooling system, the type which opens and closes by expansion and contraction of a thermal expansion material, such as wax, is broadly used. In this type of thermostat, when the temperature of the coolant therearound reaches a given opening temperature or above, the thermostat opens due to the expansion of the thermal expansion material, and when the coolant temperature falls below the opening temperature, the thermostat closes due to the contraction of the thermal expansion material. Further in the open state of the thermostat, the opening of thermostat becomes larger as the coolant temperature rises, and when the coolant temperature reaches a given full-opening temperature or above, the thermostat fully opens.
As disclosed in FIG. 1 of JP2006-273114A, a display of a water temperature meter (water temperature display) where a temperature of a coolant of an engine is displayed is usually provided on an instrument panel along with a display for a tachometer etc., and it is possible for a passenger to ascertain whether the engine is overheated and estimate the function level of a car heater based on the displayed contents in the water temperature display.
Incidentally, in a state where the thermostat is partially opened, the engine coolant is adjusted in temperature so that around the thermostat, the temperature is between an opening temperature and below a full-opening temperature. In this state, the temperature of the engine coolant is adjusted by significantly varying while repeating a frequent decrease and increase. Although there is no significant problem with such a variation of the coolant temperature itself, if the displayed contents on the water temperature display significantly vary corresponding to the coolant temperature, the passenger may feel disconcerted.
In this regard, with a water temperature meter of the conventional analog pointer type, while the detected temperature is within a given wide temperature range, even if this detected temperature varies within the temperature range, the pointer of the water temperature display is locked to point at a given temperature within the temperature range. Thus, it is prevented that the passenger feels disconcerted.
The water temperature display of the water temperature meter of the conventional analog pointer type usually has a simple design such that a plurality of temperature ranges are defined by a plurality scales, one of these temperature ranges higher than a regular-use range is colored in, for example, red, one of the ranges lower than the regular-use range is colored in, for example, blue, and the scales are not assigned with numerical values. Therefore, a specific temperature cannot be ascertained.
On the other hand, a type of water temperature meter which digitally displays on a liquid crystal display (LCD) etc., has been put in discussion or practice. For the water temperature display of this type, to respond to the needs of users toward more accurate water temperature, it is discussed in some cases to display numerical values corresponding to the scales in addition to digitally displaying scales and a pointer similar to the conventional analog pointer type.
However, in the case of providing the numerical values to the scales of the water temperature display, if the pointer is locked at a position corresponding to a given temperature similarly to the conventional type when an actual water temperature varies within the given temperature range, the pointer keeps pointing at the scale provided with the numerical value of the temperature different from the actual water temperature in this locked state, which goes against the needs of the users toward the actual water temperature. On the other hand, if the detected water temperature is displayed as it is at all times, the displayed temperature significantly varies as the actual water temperature varies within the temperature range where the actual water temperature significantly varies as described above, and the conventional problem in which the passenger may feel disconcerted even if the engine cooling system is functioning normally remains.